Aircraft are to be allowed to fly underneath dense concentrations of ash cloud
under new rules designed to prevent aviation being crippled by future
volcanic eruptions.

A radical overhaul of the guidelines was being agreed by Philip Hammond, the Transport Secretary, as the latest forecasts brought relief to around half a million air passengers whose travel plans were under threat.

Existing safety rules outlaw flying underneath the cloud, but the planned changes will mean that planes will be allowed to amend their flight paths - which could entail climbing more gently and only reaching their cruising altitude once they are clear of the ash.

While some flights would still have to be cancelled, because of the limited available air space, the revised rules would make it possible to keep a significant number of services operating.

In addition airlines, the Met Office and the Civil Aviation Authority have agreed to pool information to get a more accurate picture of the density of future ash clouds.

Met Office projections had shown that almost all of Britain was due to be covered by a dense cloud of volcanic ash tomorrow.(Fri)

But just as airports and airlines started drawing up contingency plans for the worst disruption since December’s arctic snap, updated forecasts indicated that the ash cloud would be far thinner than first thought.

The cloud, which crippled flights in Scotland and parts of northern England, caused disruption over parts of northern Europe yesterday, leading to the 700 cancellations, mainly involving flights to and from Germany.

Even though the Grimsvötn eruption did not wreak the same havoc as that of Eyjafjallajökull volcano last year, airlines were still critical of the strict rules which led to 1,600 cancellations.

It is this which has led to the planned change in the rules which will allow aircraft to keep operating even when there is a thick cloud of ash in the sky.

The Government also moved to answer criticism from airlines over its failure to procure an aircraft capable of inspecting the ash at close quarters.

It borrowed planes from Ireland and Germany to examine the ash, with the latter aircraft being made available until Britain’s own dedicated plane enters service late next month.

But last night one volcanic expert Andy Hooper, a professor at Delft University of Technology, warned that eruptions were becoming more frequent and powerful, increasing the chances of more ash reaching Europe in the future.

In addition officals from the Department for Transport and Civil Aviation Authority were examining material provided by British Airways which flew an aircraft through the red zone of densest ash on Tuesday evening.

Further material was provided by easyJet, with the airline presenting the results of its own satellite tracking.

"The new regime that we have established since last year has already significantly reduced disruption for passengers and airlines," said Philip Hammond, the Transport Secretary. " If we still had the old regime in place, the whole of UK airspace would have been effectively closed."